This invention relates to an improved piston type throttle valve carburetor with a large air inlet port used for high power internal combustion engines.
The piston type throttle valve carburetor is constructed such that a needle valve is fixed facing the throttle, whereby the fuel supply is increased by opening the throttle valve, that is, by increasing air intake, and the fuel supply for the full load operation is defined by the cross-sectional area of the main jet.
Therefore, in the piston type throttle valve carburetor for high power internal combustion engines, the clearance between the jet needle and the metering section of the needle jet must be kept extremely small when the throttle is opened only slightly, that is, when the engine is operated under light load. This means that extreme accuracy is required in machining and assembling of the jet needle, needle jet, throttle valve body supporting the needle jet as well as the carburetor body supporting the needle jet. Otherwise, it is impossible to maintain supply of the fuel-air mixture of the proper mixture ratio required for the light load operation. Further, the extremely small clearance between the jet needle and the metering section of the needle valve impairs the effect of the air bleeding and thus impairs the fuel-vaporizing performance of the carburetor.
This invention is intended to provide an improved piston type throttle valve carburetor for high power internal combustion engines, which is able to supply properly mixed fuel-air mixture in the light load operation without keeping the clearance between the jet needle and the needle jet extremely small, and thus fully utilizes the effect of the air bleeding, that is, a carburetor such as is able to supply properly mixed fuel-air mixture over the full range of operation and can be manufactured with the accuracy, in machining and assembling jet needle, needle jet, and other related parts, of the same level as that in manufacturing small size carburetors.